MIDI items delete slowly from arrange when MIDI editor open

[inthevoid]

Moving this thread to this forum as I don't think it technically belongs in 'Bug Reports'. Mods, feel free to delete my post there if it doesn't fit.

With the MIDI editor open, and with 'Active MIDI item follows selection changes in arrange view', 'Media item selection is linked to visibility', 'Selection is linked to editability' selected, and MIDI editor behaviour set to one MIDI editor per project and 'Open all selected MIDI items', multiple selected items delete slowly, one by one, from the arrange view.

To replicate the issue, using the example project I attached in this post (https://forum.cockos.com/showpost.ph...6&postcount=98), which contains no FX or MIDI notes, just tracks and MIDI items on them:

- Open the project up in a clean install of Reaper 6.73.

- Make sure 'Active MIDI item follows selection changes in arrange view', 'Media item selection is linked to visibility', 'Selection is linked to editability' are checked in Preferences > MIDI editor.

- Uncheck 'Close editor when the active item is deleted in the arrange view.'

- Hit Apply.

- Make sure 'Behavior for open MIDI items in built-in MIDI editor' > 'Open all selected MIDI items' is selected.

- Make sure the MIDI editor is set to 'One MIDI editor per project'.

- Scroll to the bottom of the arrange window, select the lowest purple MIDI item and open it up in the MIDI editor.

- Marquee select several MIDI items above it, up to the top of the orange items, for example.

- With the MIDI editor still open, hit Delete.

- The items delete slowly, one-by-one from top to bottom.

With the MIDI editor window closed, the items delete instantaneously.

Computer specs are as follows:
Windows 11 Pro (21H2)
Reaper 6.75 64-bit
RME Fireface UCX II
Intel i9-12900K 3.20GHz
64GB DDR5 RAM

GIF of behaviour attached below.